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Cranberry (Vaccinium macrocarpon)

Proposed Uses; Prevention and Possibly Treatment: Bladder Infections; Periodontal Disease, Ulcers

Prevention Only: Cancer, Heart Disease

The cranberry plant is a close relative of the common blueberry. Native Americans used for the treatment of bladder and kidney diseases.  Subsequent physicians used it for bladder infections, for "bladder gravel" and to remove "blood toxins."

In the 1920s, researchers observed that drinking cranberry juice makes the urine more acidic. Since common urinary tract–infection bacteria such as E. coli dislike acidic surroundings, physicians concluded that they had discovered a scientific explanation for the traditional uses of cranberry. This discovery led to widespread medical use of cranberry juice for treating bladder infections.

Cranberry is widely used today to prevent bladder infections, although as yet the evidence to support this use remains limited. Interestingly, studies have found that in women who frequently develop bladder infections, bacteria seem to have a particularly easy time holding on to the bladder wall.  This suggests that cranberry juice can actually get to the root of their problem.

Cranberry seems to prevent adhesion of bacteria to the bladder preliminary evidence suggests that it might also help prevent the adhesion of the ulcer-causing bacteria Helicobacter pylori to the stomach wall. One double-blind, placebo-controlled use of cranberry reduced levels of helicobacter infection in infected individuals. 

Other preliminary evidence suggests that the same actions of cranberry juice might make it useful for treating or preventing cavities or gum disease.  Before cranberry could be practical for this purpose: the sweeteners added to cranberry would have to be removed.

Cranberry has also been investigated as a possible aid in reducing the risk of heart disease and cancer, and as a treatment for diabetes, but there is no meaningful evidence as yet that it is actually helpful for these conditions.  One study failed to find that cranberry significantly effective for enhancing mental function.

What Is the Scientific Evidence for Cranberry?
The only reliable evidence for the use of cranberry juice for preventing bladder infections comes from double-blind, placebo-controlled study of sexually active women that compared placebo against both cranberry juice (8 ounces three times daily) and cranberry tablets . The results showed that both forms of cranberry significantly reduced the number of episodes of bladder infections; cranberry tablets were more cost-effective.

Three other double-blind, placebo-controlled studies evaluated the effectiveness of cranberry extract for eliminating bacteria in the urine of people with with bladder paralysis (neurogenic bladder). The results showed no benefit.

Finally, a open trial of women found that regular use of a cranberry juice/lingonberry combination reduced the rate of urinary tract infection as compared to a probiotic drink or no treatment. However, because this study was not double-blind, the results are unreliable.

Dosage
The usual dosage of dry cranberry juice extract is 300 to 400 mg twice daily. For people who prefer juice, 8 to 16 ounces daily should suffice. Pure cranberry juice, not sugary cranberry juice cocktail with its low percentage of cranberry, should be used for best effect.

Safety Issues
As a food, cranberry is thought to have a good safety profile.
Five case reports suggest that cranberry could interact with the drug warfarin (Coumadin), potentially leading to internal bleeding. However, a formal study failed to find evidence of such an interaction.  Cranberry juice might allow the kidneys to excrete weakly alkaline drugs more rapidly, thereby reducing their effectiveness. These include many antidepressants and prescription painkillers.  Indirect evidence suggests that regular use of cranberry concentrate tablets might increase risk of kidney stones.

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